Ask Paul Paez what his least favorite part of running a "one-man show" has been, and he'll answer quickly: writing and sending invoices to customers. "I hate it more than anything I do," he says. Paez's five-month-old company, Narrative Group, Interactive, which is based in Campbell, Calif., helps temporary-staffing agencies and other brick-and-mortar service companies market themselves on the Internet using techniques like targeted E-mail lists and banner ads.

Why has billing been such a pain for him? For starters, he couldn't charge for the five hours a month he spent doing it. And since Paez, 36, sells an intangible service, he had to painstakingly detail the jobs that he billed for -- everything from "trained administrative assistant how to do mass E-mailing" to "linked company URL to industry Web sites." The job was so arduous that Paez would often resort to sending out general statements, hoping that his relationships with his customers were strong enough to withstand the professional lapse, or he'd wait so long to do his billing that he'd run into cash-flow problems. "The longer I put it off, the longer it took me to get paid," he says.

He was suffering silently over the issue when, last November, he got a targeted E-mail describing a free Internet-based time-billing service from TimeBills.com, in Boston (617-351-0230; www.timebills.com; $3.95 a month per user for more than five users; enterprise pricing for more than 25 users). "It was like a godsend," he says. (TimeBills.com is one of several time-tracking sites that have cropped up on the Internet recently. Others include Elite.com, Redgorilla.com, CMSopen.com, and OnlineTimesheets.com.)

Paez immediately linked to TimeBills.com, where he created a "TimeBill" for each of his current and upcoming projects: an electronic record listing the type of project, customer name, project dates, and billing rate that he could view by date, by invoice number, or by customer. Because he regularly records his schedule on Microsoft Outlook, Paez could simply import the information from his personal digital assistant. (Users can also import the information from PalmPilots or enter it manually.) Then, as the work proceeded, he updated the record using the site's "timer" function, which with a click automatically kept track of his hours and calculated the amount the customer owed for each task.

Paez's favorite feature was the program's "EZ Invoice" function, which enabled him to create polished two-page invoices that, he says, "make me look bigger and more professional than I could on my own." The first page of the invoice contains a bill summary and a message (either TimeBills.com's own or one written by the user) explaining the purpose of the invoice, plus a detachable payment stub. The second page is an itemized bill. Paez can print out his invoices at no charge and mail them himself or E-mail them to customers as an attachment. He prefers, however, to have TimeBills mail out the invoices for a fee. (The first three are free, then it's $4.95 for every three thereafter.)

After the invoices have been mailed, Paez uses the service's "Payment" function to record and track incoming payments. He then monitors his company's financial health by examining the various statements that TimeBills.com automatically compiles from his customer data -- everything from project budgets to expensed items to an accounts-receivable report that reads like a simple aging chart, complete with the status of customers' payments.

By Paez's reckoning, using TimeBills.com saves him close to $500 a month, since the five hours (at $100 per) that he used to spend on invoicing he can now spend with customers. Then there are the cash-flow benefits: because he now sends out invoices promptly, Paez can get paid within 30 days of a job's completion date. But he's most pleased with how TimeBills.com allows him -- with little effort -- to fully spell out what his customers are paying for. "Now I can be fully accountable for my hours," he says. "It enables me to deliver more value to the relationship."